# 400 Client Error: Bad Request in flashbots.py

**URL:** https://collective.flashbots.net/t/400-client-error-bad-request-in-flashbots-py/996
**Category:** Searchers
**Tags:** question
**Created:** [January 7, 2023, 1:28pm UTC](https://collective.flashbots.net/t/400-client-error-bad-request-in-flashbots-py/996 "2023-01-07T13:28:03Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![Versus](https://collective.flashbots.net/letter_avatar_proxy/v4/letter/v/35a633/32.png) [@Versus](https://collective.flashbots.net/u/Versus)
#### Post date: [January 7, 2023, 1:28pm UTC](https://collective.flashbots.net/t/400-client-error-bad-request-in-flashbots-py/996/1 "2023-01-07T13:28:03Z")

</div>

Hello! I am using flashbots.py to simulate and distribute the bundle.  
I wrote a python script and everything worked a week ago. however now I am getting an exception:

```auto
   File "/home/u/.local/lib/python3.9/site-packages/web3/_utils/request.py", line 114, in make_post_request
     response.raise_for_status()
   File "/usr/lib/python3/dist-packages/requests/models.py", line 940, in raise_for_status
     raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://relay.flashbots.net/

```

to understand what’s going on, I modified the web3/\_utils/request.py file and displayed the request parameters:

```auto
endpoint_uri: https://relay.flashbots.net 

data: b'{"jsonrpc": "2.0", "method": "eth_callBundle", "params": [{"txs": ["0xf86d82011c850359787955825208944add366e483386870049da86548df92c661d65b1873543e44dbbf6da801ba023b0e907eb70b90e0bed1a608a8cdaeefbedd1b9b5c01b961f6131a5d1b82f05a0182eb079d0ad1792467b58da4c45c7bac28d7d01c2180f37841eaafc044c0dc2", "0xf8a90885035978795582b63294c12d1c73ee7dc3615ba4e37e4abfdbddfa38907e80b844095ea7b30000000000000000000000007a250d5630b4cf539739df2c5dacb4c659f2488dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff1ba065a53fb4a725c175b84d1fbbc9c6a0d58c271bccdf171e19908bd830721a5610a036ffedd26853c4d946710647d294a4d384343878cffb2c74c5671d3aae7e68a2", "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"], "blockNumber": "0xf98e9d", "stateBlockNumber": "0xf98e9c", "timestamp": 1673095331}], "id": 0}' 

args: () 

kwargs: {'headers': {'Content-Type': 'application/json', 'User-Agent': "Web3.py/5.31.3/<class 'flashbots.provider.FlashbotProvider'>", 'X-Flashbots-Signature': '0x2CA0aFCccf07a18c10F27de1217138b34B32494b:0x4a585ed1300fe3bd32959bed869b2763f5276c4f8cc0377cffd8c99fe044e7617bae14c681a7c5e80571f3b5fce913e35d8dfef7eff483573858ba01f853d9dc1c'}, 'timeout': 10}

```

everything is falling apart on the simulation call…

Help to understand what’s the matter, everything worked.  
I tried to generate a new access key - but it did not work.

---

<div class="post-metadata">

### Author: ![bhaki](https://collective.flashbots.net/user_avatar/collective.flashbots.net/bhaki/32/853_2.png) [@bhaki](https://collective.flashbots.net/u/bhaki)
#### Post date: [January 8, 2023, 7:22pm UTC](https://collective.flashbots.net/t/400-client-error-bad-request-in-flashbots-py/996/2 "2023-01-08T19:22:09Z")

</div>

Hi,  
I debugged your transaction. You are missing chainID in your transaction.If your transaction missing chainID then Geth converts this empty value as zero value( Comment from GETH -For legacy transactions which are not replay-protected, the return value is zero) .  
Please parse your transaction. We recently added chaindID validation check. If you are missing or sending wrong value it won’t be processed.

 ![image](https://collective.flashbots.net/uploads/default/original/1X/b09a707877d7866f55900dd1d87708cd7bdf5907.png)

Also will check the python client to fix parsing issue if needed.  
I agree error translation are little bit harder as errors can not be updated now for legacy reason.  
Thank you for reporting. But going forward, please report it in discord. I usually respond or some one/other searchers will help you there or tag me @Euler6.

---

<div class="post-metadata">

### Author: ![Versus](https://collective.flashbots.net/letter_avatar_proxy/v4/letter/v/35a633/32.png) [@Versus](https://collective.flashbots.net/u/Versus)
#### Post date: [January 8, 2023, 9:12pm UTC](https://collective.flashbots.net/t/400-client-error-bad-request-in-flashbots-py/996/3 "2023-01-08T21:12:32Z")

</div>

Hello. Thank you very much!  
Everything worked!  
The problem was the lack of chainId. Should have made a separate error code for this case 🙂